The immediate aim of this research proposal is to develop an economic method to produce the maytansinoid DM1 for subsequent conjugation to monoclonal antibodies (mAb). Drugs of this type are undergoing preclinical development as cancer cell targeted antitumor drugs. DM1 currently is produced by semisynthesis from the fermentation product, ansamitocin P3 (AP3), at a cost exceeding $10,000/gram. Reduction in the cost of DM1 to approx. $1,000/gram is feasible and would encourage broader exploration of its use as a mAb conjugate in cancer treatment. In Phase I work, we will pursue the following specific aims: (1) Explore and discover more efficient and economic chemical or enzymatic methods for conversion of AP3 to ansamitocin P0 (APO). (2) Explore and discover the most efficient and economic chemical method for the synthesis of DM1 from APO that avoids racemization of the chiral center in the N-acyl-N-methyl-L-alanine moiety of DM1. (3) Create an AP3 overproducing strain by overexpression of the asm18 gene that positively controls expression of AP3 biosynthesis genes. The long term goal of our research is to develop a large scale process for manufacturing the amount of DM1 needed for clinical trials and cancer treatment at a practical cost. PROPOSED COMMERCIAL APPLICATIONS: The research will provide an economic means to produce large amounts of the semisynthetic cytotoxin, DM1, that when conjugated to tumor cell specific monoclonal antibodies (mAb), has shown remarkable efficacy in cancer therapy. DM1-mAb conjugates are undergoing preclinical development in the pharmaceutical industry and are likely to enter clinical trials within the next two years. Therefore, a successful outcome of our research would meet the needs for preclinical and clinical development at a far lower cost than the current DM1 synthesis that is the only source of this cytotoxin.